You can refer to the definition here:
https://www.canada.ca/en/services/immigration-citizenship/helpcentre/glossary.html#maintained-status
Maintained status (while processing an application)This is a legal extension of status that allows temporary residents to stay in Canada while we process their application. To be eligible, the temporary resident must apply to extend their status before it expires. This used to be known as “implied status.”
Once you file your application and IRCC acknowledges receipt of your application, you are under “implied status”. Basically having the same rights as that of an approved application (until such time that decision has been made).